Cataract extraction is a frequently performed surgical procedure. A cataract is formed by opacification of the crystalline lens of the eye. The cataract scatters light passing through the lens and may perceptibly degrade vision. A cataract can vary in degree from slight to complete opacity. Early in the development of an age-related cataract the power of the lens may increase, causing near-sightedness (myopia). Gradual yellowing and opacification of the lens may reduce the perception of blue colors as those shorter wavelengths are more strongly absorbed and scattered within the cataractous crystalline lens. Cataract formation may often progress slowly resulting in progressive vision loss.
A cataract treatment may involve replacing the opaque crystalline lens with an artificial intraocular lens (IOL), and an estimated 19 million cataract surgeries per year are performed worldwide. Cataract surgery can be performed using a technique termed phacoemulsification in which an ultrasonic tip with associated irrigation and aspiration ports is used to sculpt the relatively hard nucleus of the lens to facilitate removal through an opening made in the anterior lens capsule. The nucleus of the lens is contained within an outer membrane of the lens that is referred to as the lens capsule. Access to the lens nucleus can be provided by performing an anterior capsulotomy in which a small round hole can be formed in the anterior side of the lens capsule. A primary incision and a sideport incision may be placed in the cornea to allow access for the ultrasonic tip or other instruments and to permit removal of the lens pieces. An arcuate incision may also be placed in the cornea during cataract surgery to alter the refractive properties of the cornea. After removal of the lens nucleus, a synthetic foldable intraocular lens (TOL) can be inserted into the remaining lens capsule of the eye.
Accurate placement of a capsulotomy incision, a primary incision, a sideport incision and an arcuate incision can be important for achieving a successful outcome of cataract surgery. In automated laser surgical procedures, physicians generally provide the necessary parameters for identifying the number, placement and size of incisions based on pre-treatment measurements. However, errors in data entry or lack of proper calibration of the laser surgical system can potentially lead to the placement of incisions at locations other than at the locations prescribed by the user. Moreover, some laser surgery systems have not allowed real time confirmation of the location of the incision at the predetermined location or have not provided warnings to the user if the actual placement of incisions during an automated scan is different from the intended location of the incisions.
Thus, methods and systems that introduce additional safeguards, such as verifying the location of a laser scan or ocular incision, would be helpful for treating patients with laser surgical systems.